Oxonium Ions from Aqua Regia: Isolation by Hydrogen Bonding to Crown Ethers

The preparation and structures of a variety of oxonium ion tetrachloroaurate(III) salts isolated from aqua regia
are reported. The new compounds are [(H5O2)2(12-crown-4)2][AuCl4]2 (1), [(H7O3)(15-crown-5)][AuCl4] (2),
[(H5O2)(benzo-15-crown-5)2][AuCl4] (3), [(H3O)(18-crown-6)][AuCl4] (4), [(H5O2)(dibenzo-24-crown-8)][AuCl4]
(5), [(H5O2)(4-nitrobenzo-15-crown-5)2][AuCl4] (6), [(H3O)(4-nitrobenzo-18-crown-6)][AuCl4] (7), [(H11O5)(tetrachlorodibenzo-18-crown-6)2][AuCl4] (8), and [(H7O3)(dinitrodibenzo-30-crown-10)][AuCl4] (9). A significant
correlation between the degree of proton hydration and crown ether size is observed. Aryl crown ethers are nitrated
in concentrated aqua regia, but nonnitrated products may be obtained in a dilute solution of aqua regia by reaction
with aqueous HAuCl4.

本文报道了一系列从王水（aqua regia）中分离得到的氧鎓离子（oxonium ion）四氯合金(III)酸盐（tetrachloroaurate(III)）的制备方法与晶体结构。所得新型化合物包括[(H₅O₂)₂(12-冠-4（12-crown-4）)₂][AuCl₄]₂（1）、[(H₇O₃)(15-冠-5（15-crown-5）)][AuCl₄]（2）、[(H₅O₂)(苯并-15-冠-5（benzo-15-crown-5）)₂][AuCl₄]（3）、[(H₃O)(18-冠-6（18-crown-6）)][AuCl₄]（4）、[(H₅O₂)(二苯并-24-冠-8（dibenzo-24-crown-8）)][AuCl₄]（5）、[(H₅O₂)(4-硝基苯并-15-冠-5（4-nitrobenzo-15-crown-5）)₂][AuCl₄]（6）、[(H₃O)(4-硝基苯并-18-冠-6（4-nitrobenzo-18-crown-6）)][AuCl₄]（7）、[(H₁₁O₅)(四氯二苯并-18-冠-6（tetrachlorodibenzo-18-crown-6）)₂][AuCl₄]（8）以及[(H₇O₃)(二硝基二苯并-30-冠-10（dinitrodibenzo-30-crown-10）)][AuCl₄]（9）。研究发现，质子水合程度与冠醚环尺寸之间存在显著相关性。芳基冠醚在浓王水中会发生硝化反应，而在稀王水中与四氯合金(III)酸（HAuCl₄）水溶液反应时，可得到未硝化的产物。